The present invention relates to improvements in machines for the production of rod-shaped smokers' products, and more particularly to improvements in machines for the production of filter cigarettes or other types of rod-shaped articles which contain tobacco and which are provided with a recess adjacent to, or with at least one cavity between, their rod-shaped components, e.g., with a cavity between the tobacco-containing and filter-containing portions. The cavities can be disposed between pairs of identical or different rod-shaped components of smokers' products, e.g., between the filter plug and the plain cigarette of a filter cigarette of unit length or between two identical or different filter plugs in the composite mouthpiece for a filter cigarette, cigar or cigarillo.
It is well known to provide cigarettes with recessed filters, with cavities between discrete rod-shaped components of filters or with cavities between the filter plugs and the tobacco-containing portions. Reference may be had, for example, to commonly owned U.S. Pat. Nos. 3,010,457 (Schubert), 3,368,460 (Schubert) and 3,817,158 (Wahle). It is also known to provide the wrapping material around the cavities with holes in the form of perforations which serve to admit metered quantities of cool atmospheric air into the cavities so that the air mixes with and dilutes and cools the column of tobacco smoke flowing into the smoker's mouth. This is believed to result in deposition of a high percentage of condensable ingredients of tobacco smoke in the cavity proper, i.e., before the smoke reaches the mouth, so that the filter merely performs a secondary or auxiliary cleaning function. Many makers of cigarettes believe that such mode of influencing tobacco smoke on its way from the tobacco-containing portion of a cigarette into the mouth of the smoker is likely to guarantee a more predictable and more uniform filtering action, not only immediately after the cigarette is lighted but also during combustion of the major part of or the entire tobacco-containing portion.
The manufacture of smokers' products with recesses behind the rearmost rod-shaped components or with cavities between neighboring rod-shaped components presents many problems, especially if such products are to be manufactured in modern high-speed machines which are designed to turn out in excess of 7000 articles per minute. The main problem is that presently known machines for the mass production of filter cigarettes, papyrossi and analogous recessed or chambered smokers' products are incapable of ensuring that the width of recesses or cavities in each of a large number of articles will be the same. If the depth of a recess or the width of a cavity is less than desired, the quantity of air which can be admitted into tobacco smoke is insufficient to ensure adequate circulation and agitation of smoke, intermixing with atmospheric air and/or deposition of condensate in the recess or cavity. If the cavity is too wide or the recess is too deep, the length of the tobacco-containing portion is less than prescribed or the composite filter of such an article lacks one of its components.